Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: greensleeves on 10/02/2011 17:43:28

Title: Was the Black Death really Bubonic / Pneumonic Plague?
Post by: greensleeves on 10/02/2011 17:43:28
The Black Death of the mid 14th century was a disease like no other in recorded history (as far as I am aware). After originating in the Far East, it spread across Asia and the whole of Europe within about 5 years. In England alone in the space of just 3 years it wiped out perhaps half the population. The same is true of the rest of Europe. Black Death is usually thought of as bubonic or pneumonic plague, and yet later outbreaks of this disease in the same century, in Elizabethan times, and of course in 1665 - although deadly - reaped nothing remotely comparable to the death toll of 1348-1350. Why was this? In later centuries medical control and prevention had not I think progressed significantly, and the population was greater and denser, and mobility around the countryside was presumably greater, so one would have expected more rapid spread and more deaths, not less. So why was the death toll in the mid 14th century so high, and so rapid? Could a flea/rat borne disease really have spread so fast? Why did it not prove so devastating in later outbreaks? Was indeed, the Black Death definitely caused by plague, or could it have had a more virulent cause?
Title: Re: Was the Black Death really Bubonic / Pneumonic Plague?
Post by: Bill.D.Katt. on 11/02/2011 05:15:35
I would say that it caused such massive devastation the first time around for two main reasons. First, the cities were very dirty and the rat population was huge (and yes, it can spread very rapidly), second, tolerance to the disease was probably extremely low at the time because the disease wasn't properly dispersed throughout the population before hand. There is a specific set of genetics that makes a person immune to the disease, I will have to do more research to remember what it is though. In later outbreaks, more people had the tolerance and therefor survived. I'm pretty sure it was the plague, all records of the time seem to point that way.
Title: Re: Was the Black Death really Bubonic / Pneumonic Plague?
Post by: greensleeves on 11/02/2011 18:16:09
Thanks a lot for your reply. As far as the first point is concerned, were the cities really dirtier and the rat population larger in 1348 than in later centuries when the disease recurred? I really would have thought that in the 14th century, Europe was largely composed of rural-based populations with lower concentrations of people. In addition human mobility across the land, and trade (including shipping trade which first brought the rats), would have been less significant than in later centuries. In these circumstances I would have thought disease spread would have been slower in the 14th century than in later centuries.

I certainly take the second point you make about increasing levels of immunity after the Black Death. Perhaps a degree of genetic immunity did develop after the Black Death - one knows that in slightly similar circumstances, relatively minor Western diseases can be lethal to native peoples when they are first exposed to them and before they develop immunity. But can such immunity exist in the population from generation to generation to protect the population from such devastating life loss, as must have happened in the centuries which followed the 14th?   
Title: Re: Was the Black Death really Bubonic / Pneumonic Plague?
Post by: Bill.D.Katt. on 12/02/2011 00:02:25
It is my strong belief that people equate to more dirt, so more people means more dirt.

Yes, I think it can. This is probably a good example of survival of the fittest, and the passing down of stronger genetics from parent to progeny.
Title: Re: Was the Black Death really Bubonic / Pneumonic Plague?
Post by: greensleeves on 13/02/2011 22:51:41
Thanks Bill. After thinking about it, I think you are right about the passing down of some immunity from generation to generation, with disease tolerance very low in the 14th century, and higher during subsequent outbreaks.

But the other part of the equation still bothers me - I can't say I know much about population statistics of our ancestors (or rats for that matter) but was Europe more densely populated in 1348 than in - say - 1665? And 'dirtier', with a greater rat population? I would still have thought disease spread would have been more rapid in later centuries, even if mortality rates might be lower for the genetic reasons you suggest.

Maybe however, like humans, the rats themselves developed some immunity to the microbe which causes bubonic plague, so less rats carried the disease?
Title: Re: Was the Black Death really Bubonic / Pneumonic Plague?
Post by: Bill.D.Katt. on 15/02/2011 00:26:20
I think disease spread, even in the early part of the second millenia, could be extremely fast. Think of how fast a ship traveling from Greece could reach London. That is how fast the disease could spread. Considering that a third of Europe died, I would have to say that it was less densly populated, although that could depend based upon population growth rates. I think during the renaissance the cities became a little more clean as well.

That could be quite possible, but if something is immune, that doesn't mean that it doesn't carry the disease for a short period of time.
Title: Was the Black Death really Bubonic / Pneumonic Plague?
Post by: greensleeves on 24/02/2011 00:04:32
In addition to Bill's points, I've just come across some other interesting ideas about the Black Death. Apparently climate change - warm damp weather in Asia - led to a proliferation of rats in the early to mid 14th century. In addition, famine in Europe around the same time which killed maybe 10% of the population, may have weakened the remainder and rendered people more susceptible to suffer the worst effects of infection.

I still find the pan-Eurasian death toll of the Black Death quite strange when related to later, more localised outbreaks, but maybe if it was bubonic plague, then the people of the mid 14th century were just extraordinarily unlucky in that a whole host of factors conspired to make them particularly vulnerable to a plague of rats, a plague of fleas, and the disease which they both carried.